Doesn't matter if it's voluntarily taken or not.
Altering someone else's mind is a violation.
Besides, you've never heard of someone drugging someone's drink? Choosing to drink something doesn't mean you willfully and knowingly consent to everything that's in that drink.
Actually with mind magic permission is everything otherwise the gatekeeper could not even start helping Peabody's many victims.
So even if the potion is mind altering (not according to the rpg as quoted earlier) and even if there is no difference between giving someone a potion to drink and using magic directly (there might be no moral difference if you deceive someone into drinking it but the laws of magic are not about morals and technicalities can make a huge difference, that is why the wardens can use magic swords to kill people)
Even then there is consent. If you tell someone what the potion is and what it does the consent is everything. With consent it is not an invasion. It can be seen as a medicine in certain circumstances.
Besides if you make a potion bomb you can kill people but if you use it on fairies it is ok. So you just say to the next warden those love potions are for use on fairies. Or for your own consumption, it certainly will cure your shyness, maybe in small doses it will just give you some courage to do what you want to do anyway.