It won't be too long before most "soft" drugs are entirely legalised in Europe, rather than the semi-official turn a blind eye policy on cannabis and the like that exists now in many places (save for The Netherlands that fully legalises and regulates). From that point, I think eventually all drugs will have some form of official registration and distribution channel and a more sensible management approach to the issue of drugs will evolve. Fighting a "War on Drugs" is like fighting a "War on Gravity" - it will cost billions, last forever and never succeed.
Immigration is much the same - so long as a group of people with nothing to lose exists who can make more money in another country than at home, they will migrate, legally or illegally. Impossible to stop this simple economic truth. As with drugs, don't fight it but manage it. Give all current illegal immigrants anmesty and access to social benefits provided they register and pay their dues and taxes. Heavily penalise employers of illegals but incentivise them to help convert their illegal to legals.