On February 10 2009 a new law goes into effect for anyone selling physical items for children under the age of 13. Each item must be tested for lead content and you must provide a certificate showing the item has been tested and is safe.
From what I gather this new law covers any and everything that is for kids; games, toys, books, clothing, furniture, jewelry etc.
The new law also makes no distinction of new, imported, recycled or used items. They must all undergo testing.
If this is a niche you're involved with, I suggest you familiarize yourself with the new law as non-compliance is a felony with some very fines.
As written, it would have the effect of halting the sale of used childrens products by 2nd hand shops, eBay and even charities (Goodwill, Salvation Army stores) at a time when more families are forced to buy used apparel.
A large manufacturer of new kids products could test and certify their output. But there's no way a resale shop could economically test one-of-a-kind used clothing.
I believe that 100% cotton or wood (?) apparel was exempted recently.