Radwraith said:

So…

it's within the realm of possibility that he's mugged 2+ Space Marine Chapters for their rides? And is now using them in Imperial Space?

The problem isnt how many, it's that they are land raiders at all.

Someone argued that he's gotta be rich - he's able to commit 2 Light cruisers to a war zone. Sorry, that's not terribly intimidating. Half the RT groups I see out there have multiple capital ships. It's a very nice investment and often they are 'free' from boarding actions.

tygre said:

This.

Without knowing all the specifics, it kind of matters where the LR's were acquired, under what circumstances, and what the RT is doing with them. If I am a Rogue Trader, and I find some salvageable Land Raiders out in the Expanse, they are mine, and the Ad Mech, the IG, the Navy, and even the Astartes can suck a big one. As a Rogue Trader, I have salvage and claim rights, and if I can get them fixed out in the boonies, the Space Marines would have to come out here and get them, dropping missions, sinking resources, what have you. They'd also have to find out about it, at all, and with the communications of the Imperium being what they are, I actually find that rather unlikely. If they do come for them, who are they to challenge me? A Rogue Trader is practically an Inquisitor, in his authority over his purviews, and as much as the DW people will say "well, the Inquisition can ask a Space Marine to…, but they cannot ORDER him to.", it goes the other way, too; a Space Marine, a Chapter Master even, has no right to command an Inquisitor, or me (a RT), another individual empowered by the Emperor, directly. He can ask me, and a favor of the Astartes is no small thing, and if I give them all but one, and get to keep it for group personal uses, I'd even be rather agreeable (I'm not quite as money-hungry as a RT should be, personally), but unless they are willing to threaten me, pull out SM ships from other engagements, load up their Space Marines from other tasks, and fly out into the benighted stars to take them, I get to do what I want. If I am really lucky, I might find Chaos LRs, and if they can be purified, then even the SMs can't really lay claim to them.

As for wealthy, many Rogue Traders have more wealth than many planets. To quote, but paraphrase, "You're a corporate CEO, Xanatos, not a country. Yes, but my company, Detective, is larger than most countries you can name." Even a Light Cruiser can cause damage to a planet a swarm of Land Raiders couldn't hope to contribute to, and a ship, any ship that can warp travel, is probably a relic on par with a Land Raider, equally full of dodgy tech the Ad Mech isn't certain they'll still be able to manufacture tomorrow.

Now, much of my blabber DOES lose some steam if they come into the Imperium, but they aren't likely to use these tanks inside Imperial borders, that's not what Rogue Traders are about.

Remember as well that SM chapters are wiped out and lost occasionally.  They might come from a chapter that no longer exists.

venkelos said:

The thing is that Astartes commanders may not be able to order you, but they can sure as hell kill you - and they hold grudges oh so well, for centuries or even millenia. If you piss of a chapter by refusing to return their Landraiders, then not only have you passed up the opportunity to be owed a favour by the Emperors finest, and the massive prestige associated with such dealings, but you have also signed the death warrant of your entire lineage, whether it is today, a year from now or many centuries down the line. Those Astartes WILL come for you and there WILL be a reckoning, no matter where you hide.

Also why on earth do you need Landraiders? They aren't all that much more awesome than Imperial guard tanks and superheavy tanks, which are far easier to acquire and maintain and don't carry the headache of being proscribed assets for a human to own.

Kasatka said:

There's a ton of flawed premises within that argument. For instance

1) Astartes would be aware of the Land Raiders.- Probably not, because the likelihood of a Rogue Trader working in a warzone (such as where Space Marines operate) is fairly low, since there's rarely a profit to made made there. 

2) Astartes would view them as "their" Land Raiders.- Probably depends on the Chapter, but since under Codex Astartes doctrine LRs are only used in specific circumstances, they'd probably have surprising little need for additional LRs.

3) Signing a death warrant of your entire lineage.- Yes, because Astartes have NOTHING BETTER to be doing than shipping off extremely valuable Marines to pursue vendetta against an Imperial citizen rather than dealing with the innumerable heretical, chaotic, and xeno threats. A grudge, yes, but dispatching a squad to hunt them down? I don't see that happening. 

4) The idea that Astartes are vendetta soliders who will bring a reckoning.- At a fundamental level Astartes are Imperial soldiers, serve the Emperor, and duty is foremost in their minds. While you seem to think possession of LRs is as good as being a heretic, I doubt that's the case. Again, if it's a choice between hunting and killing threats to the Imperium vs. chasing what is still technically another loyal servant of the Imperium, they're gonna always choose the actual threat, since even if a RT having LRs is a weird idea, the RT is still furthering Imperial cause with said vehicles.

Are there Chapters that would probably invalidate what I said? Probably yes, because there's always an exception in 40k. But I think the situation you outlined is ridiculously unlikely and paints Astartes in a way that is very untrue to the majority of their depictions. 

I think the real question here is:

Who the hell is going to tell a Rogue Trader with THIRTY LAND RAIDERS! that he is not allowed to have them?

Space marines may be good, but their role is mostly poster boys for the imperium.  A chapter contains a mere thousand marines. Even the smallest voidfaring ships have upwards of TENS OF THOUSANDS of crew. Do you honestly think a chapter of space marines has any real chance against a large dynasty with millions of men at arms?

Space marines may be the best troops that the imperium has to offer, but if you shoot their spaceship out of the sky, it won't do them much good. Chapter Masters are not stupid. They will grumble, then they will tuck their tails between their legs and go home. Rouge traders are that powerful.

Well, how many Landraider fit into a Landraider Battalion?
I would say somewhere between 3 to 9.

True that is a lot of landraiders and if the RT Dynasty salvaged them he has rights to them. The Space Marines might be powerful but so is a RT Dynasty. 
The Landraiders might have been in the possession of the Dynasty before the age of Apostacy, which would make them his by any right, some Dynasties are that old.

So a RT could possibly have a small group of landraiders legally. Some chapter might nog like it, but they would swallow their pride because the RT can provide much needed warships.

 @HTMC - Of course there will always been something to prove and something to disprove and argument in the 40k setting, but there is enough published material in novels of astartes chapters pursuing vendettas that virtually wipe them out over some trivial slight in the ancient past that i feel my point is valid.

@Fireinthahole - A space marine chapter master isn't going to just send a couple of marines against you, nor will a rogue trader ever have 'a million armmen' to hand, the books suggest 10% of a ships crew would be armsmen, which would be 6 or 7 thousand on a cruiser. The Astartes would have rapid strike vessels, frigates etc that can track down any vessel an RT could captain, and marines excel at boarding actions enough to not really care how much damage you do to their vessel, cause once on board they will either gain control of your ship or heavily cripple it to the point everyone has to evacuate.

 Okay,

I know everybody sees the Space Marine as the epitome of absolute coolness and bad ass-ness of the 40k setting. And while they might be god like in battle they are not that good. They are extremely spread out and have very few numbers, they are poster boys.

No Chapter Master in his right mind would risk attacking a mighty RT Dynasty in Space. If a ship with 100 marines on it is blown up, it is a tremedous loss which might take centuries to recover. 
If they wanted to make claim on the landraiders they would open negotiations. Offer the RT compensation, they would trade. Why would they attack such mighty possible ally. The marines have plenty of enemies, they have relatively few allies. And how valuable would an alliance with a Rogue Trader Dynasty be for the Chapter. Rogue Trades have ships, which can provide great firesupport and they are good at space battles, they can escort the Strike Cruisers through a blockade so the marines can land on a target planet.

Space Marines are the Imperiums finest warriors, Rogue Traders…are TRADERS, everything has a price!
 

Santiago said:

Actually if you look at the profit factor bit in the core Rogue Trader book it gives you some examples of other agents of the imperium and their equivalent profit factor. I think you'll find an entire Astartes chapter has more clout than a single inquisitor, and an inquisitor has more clout than a low to mid level RT. Regardless, an RT only has so much power at his fingertips, some of his dynasty is always going to be found back within the Imperium, be it accountants, vaults, relatives etc. All of these things could be targetted by a chapter looking to get some Land Raiders - and what chapter wouldn't?! Most chapters either have very few if any Land Raiders and so would want some, or already use them and would benefit from having more in reserve.

Kasatka said:

OK: deep breath…

One: Space Marines can and do lose boarding actions against regular armsmen. 

Two: An astartes rapid strike vessel is no more heavily armed then a regular frigate, and has about a squad of marines aboard.  Due to their very limited ranges and the Codex AND Inquisition AND Navy's prohibitions against the Astartes having ships capable of an even engagement against ships of equal tonnage, a SM chapter is at it's weakest in a ship to ship engagement, which is where Rogue Traders and the Navy excel.

A SM strike cruiser, as an example, presents a variety of threats, BUT is only any good because it's very adaptable and heavily armored.  As far as firepower goes, it's miserable even compared to many other light cruisers.

There is a REASON that the Space Sharks considered a grand cruiser to be the equal of a battle barge, even though the battlebarge is in the same weight class as most battleships.