1) If drugs were legal, there would be more room in prisons for violent offenders. With more prison beds available, we would be less likely to parole, or release early, violent offenders that should be kept out of the public. Judges would also be more likely to sentence violent offenders to more significant prison terms.
2) The government (local, state, and federal level) would save billions of dollars. By not funding a losing war on drugs, we'd save a boatload. That money could be spent on other law enforcement activity like protecting our borders, anti-terrorism, finding bin Ladin, citing speeders, arresting DUI drivers or whatever.
3) The government could make money by taxing the drug trade.
4) If drugs were legalized, there'd be less violence related to illicit drug trade. If your drug of choice were sold over the counter at the 7-11 store, the streets would be safer.
While the points here are not necessarily mine, I've heard all of these arguments before and I'm inclined to think that there is at least some truth to each one. I realize that there is a technical difference between legalization and decriminalization. For the sake of keeping it simple here, I consider legalizing to be similar to the way the government treats alcohol. In most places in the country ( except Pennsylvania) alcohol can be purchased in stores. Taxes are levied on alcohol sales, and there is a minimum drinking age (21).