As of right now, it's legal to use the combination of Mean Look/Spider Web + Baton Pass in GSC OU. Unlike in generations 5 and up, the trapping effect gets passed to the recipient here. Three Pokemon have access to this strategy; Ariados, Smeargle and Umbreon. The latter two of which being the biggest team building headaches in the tier by far, in my opinion.
Starting with Smeargle, the main problem in dealing with it is that it's usually one of two main sets that you're facing; Spikes or Baton Pass. Baton Pass sets can either be Spider Web or a boosting move like Agility, with the noteworthy difference being that Mean Look and Spider Web are already banned in conjunction with Sleep inducing moves. This means that it essentially comes down to Smeargle either having Spore or Spider Web, and therein lies the issue. If you go to a Sleep absorber like Sleep Talk Zapdos or Snorlax, you're well off into Spore sets, but could instantly lose the game to Spider Web Smeargle passing the trap to something like Curse Snorlax or starting up a full chain. If you go to a phazer or Explosion/Self-Destruct Pokemon to prevent that from happening, you're risking getting taken out of the game by Spore instead. 'Choosing' wrong could end your game on turn 1.
Umbreon doesn't learn a Sleep inducing move like Smeargle, but still has plenty of tricks up its sleeve to completely disrupt its counter play. The nastiest of those tricks is by far Confuse Ray, which reduces your chances to escape the Mean Look + Baton Pass trap to simply not hitting yourself two turns in a row. If you do and Umbreon successfully passes out against your Roar Steelix or Golem, for example, Pokemon like Cloyster and Vaporeon come in freely, click Surf and you're cooked. To make matters worse, Umbreon can often use (nearly) all of its Mean Look PP trying to pull this off, as it's very bulky and you have to go to your phazer every time. Umbreon also commonly runs Toxic to ruin phazers like Tyranitar, Golem and Rhydon, which you're basically forced to switch into Umbreon, because you can't chance a Mean Look being passed into a sweeper that farms better answers to Toxic.
This strategy is needlessly cheesy, makes for stupid games and painful team building hurdles, especially around Smeargle. I know banning Baton Pass outright is still a bridge too far for most GSC players, but can we please ban the passing of Mean Look and Spider Web as soon as possible? If they can't be used alongside Sleep moves, then surely this is a reasonable combination to axe as well.