In the old days "cross-compliance" simply meant if you participated in the program for crop A on your farm you couldn't expand your acreage of crop B. ("Offsetting compliance" meant you could n't expand your acreage on other farms if you participated in one farm.
These days "cross compliance" refers to sod/swamp, and it's controversial. A set of organizations sent a letter asking for no cross compliance. Former NRCS chiefs sent a letter supporting it.
The requirement was in effect from 1986 to 1995. I suspect, but don't know, that it wasn't very effective. SCS and ASCS had big problems working out how to enforce it and I suspect FCIC/RMA was never much involved, at least until well into the 90's.
In thinking about the possible problems with such a provision, a good part of the problem is timing. Ideally the first contact a farmer has with a USDA agency, including crop insurance agency, should involve a checking of the conservation compliance status for the farmer's operation. If she has highly erodible land is there a conservation plan of operation in place and up-to-date? If there's wetland, what's the status? If there's a problem, the farmer needs to fix it or bypass crop insurance. In the 90's sharing access to that information would be difficult because it wasn't all in one place. These days it should be technically feasible, if probably still bureaucratically difficult.
I wonder if crop insurance is subject to the administration's Do Not Pay rules?