I cannot understand the usage of words in bold; please comment on it.
Thank you in advance.
U.S. President Barack Obama signed more sanctions against Iran into law on Saturday, shortly after Iran signaled it was ready for new talks with the West on its nuclear program and said it had delayed long-range missile tests in the Gulf.
(Iran navy tests surface-to-air missile in drill - World news - Mideast/N. Africa - msnbc.com)
See #9 here http://bensguide.gpo.gov/9-12/lawmaking/index.html
Once the president has signed the bill (in your case, imposing sanctions) it becomes law. It is transformed from not-law into law by his signature.