It is not over Lvl 75, and I've lost the instruction booklet. If it is Lvl 30, thats a little daft, because I'm nowhere near Saffron for my next badge, and my pokemon are bursting at the seams to level up over 30.
Level 30....But your pokemon will still obey you if you've had them for a long time even if they pass level 30...The reason Nintendo has this is to prevent trainers from switching over level 100s after you get your first pokemon.
Actually, there's no level boost from Surge's badge. Misty's badge allows them to go up to lv.30, Erika's up to lv.50. Surge just boosts your pokémon's stats.
The only Pokemon that apply to the badge rule are Pokemon from a different game, and in game is pretty simple without trading at all, so there's no need to worry.
Any pokemon that you've caught in this game will still obey you even if they exceed level 30, but traded pokemon will only obey you if they're below level 30.