No right-minded person could have disagreed with Sen. Jane Nelson, R-Flower Mound, when she said last week, "Taxpayer dollars should not be used to subsidize a person's drug habit."She was talking about SB 11, a bill she pre-filed in advance of the legislative session that begins Jan. 8. Among other things, the bill calls for drug screening and some mandatory drug testing of people who apply for a key social welfare program, Temporary Aid to Needy Families.Gov. Rick Perry chimed in at a news conference."Bottom line," Perry said, "is that illegal drug abuse is not something Texas taxpayers will ever subsidize or tolerate."So SB 11 is both a get-tough-on-welfare-abusers bill and a get-tough-on-drugs bill. Nothing wrong with either thrust, not if they're executed properly and fairly.But it's rare that any bill is finally passed by the Texas Legislature as initially filed. That's a good thing, because it would be embarrassing to have 181 elected representatives of the state's more than 26 million residents working on something for five months and not be capable of making it better.Lawmaking shouldn't be easy. Many bills fall by the wayside between early January and late May of each session because they turn out not to be the great idea they initially seemed.What could go wrong with SB 11? It's usually a good idea to look first at the assumptions inherent in a bill.This one starts out with a negative view of TANF recipients, who only qualify for these funds because young children in their home need food and clothes. If we're going to make assumptions about them, let's assume that most are people who love their children and would never do anything to harm them. Like most of us.There seems to be an assumption, not yet proven, that an appreciable number of TANF recipients spend the government's money on drugs. There may be a problem, but if there is it should be evident from statistics showing an appreciable numbers of TANF recipients in the past having been arrested on drug charges.Nelson should show those statistics to her legislative colleagues and the rest of us. Keep in mind that TANF recipients must already pledge not to abuse alcohol or drugs, so arrest statistics should also show up in numbers of people expelled from the program for that reason.SB 11 would require that applicants for TANF or for the renewal that's required every six months be screened for possible drug abuse, presumably through a face-to-face meeting with a caseworker. Those who are suspected of drug abuse would then be required to take a drug test.Testing positive for any controlled substance for which the applicant has no physician's prescription is an automatic disqualifier, and child welfare workers are to be notified of possible danger to the applicant's children.No extenuating circumstances are considered. An applicant who puffed on a marijuana joint at a party is treated the same as a hard-core heroin or methamphetamine addict.These are harsh steps. They should be shown to be necessary before this bill is passed, and they should be shown to be the least restrictive steps necessary.By definition, denial of TANF benefits on the basis of a drug test alone would mean children who need help won't get it -- or may be separated from their parents. Caution, not assumptions, is required.