Rusty,
There are now quite a few checks that need to be done, the responsibility has been shifted from the UKBA (COA) to others. Nothing is 100% of course, but those who have authority to organise marriage are now much more aware of the legal requirements and consequences of failure to comply with regulation. First requirement is valid visa.
Even if they somehow managed to get married, they could not legally progress any leave to stay within current immigration rules.