Rules.ini file changes doesn't affect the Single Player campaign?

[F.E.A.R.]

So I tried changing the rules.ini file such as, how many units I can build and the Power Plant power, however this doesn't work on SP only on Skirmish. Is there anyway to get it working on SP?

[XMaDTanKX aka T-90]

There are two rules files, rules.ini and rulesmd.ini, one for Ra2, one for YR, by that order

Firstly make sure you have modified the right one.
And secondly, it could be that the campaign modes doesn't use the rules.ini in the main folder but the one located in local.mix, and also most of the singleplayer maps have modified own .ini settings, having preference over the settings in main rules.ini

Edited March 9 by XMaDTanKX aka T-90

[F.E.A.R.]

I actually found out. Changing the rules.ini file for Tiberian Sun does effect the campaign, you just need restart the game and load from a previous near to end mission and the changes will take effect in the next mission.