Members of congress are convinced now is the time for a full-scale inquiry linked to Russia's alleged interference in the 2016 election.
Experts say buying homes for cash and then later taking out mortgages can raise suspicions.
Banking sources said some transactions raised sufficient concern to trigger an internal investigation into potential money laundering activities.
More than 33,000 people died from opioids, which include prescription painkillers and heroin, in 2015. The CDC calls it an overdose epidemic.
The signature comes nine months after voters in Britain decided to leave the European Union. The process could take up to two years.