There have been several attempts to pass legislation in the United States to ban internet gambling, but the attempts have failed.  Currently there are no federal laws criminalizing placing bets online. 

The Federal Wire Act prohibits the placing of bets across telecommunication lines, but it does not mention the Internet.

The biggest piece of legislation to address the issue came in 2006 under the name of the Unlawful Internet Gambling Enforcement Act (UIGEA).The UIGEA did not target individual players. Instead, it targeted banks and payment processors by restricting the funding of online gambling sites. Any company that funded gambling payments was targeted, but the actual act of betting was never addressed.Many banks argue that the UIGEA places an unreasonable burden on banks to identify specific gambling-related transactions among the millions of transactions they process on a day-to-day basis.

The World Trade Organization has handed down satisfying rulings against the United States’ stance on online gambling. The WTO has ruled over the past few years that the USA ban on Internet gambling violates international trade agreements.The basis of the complaint is that US companies are allowed to provide online horse betting while foreign companies cannot. The policy is protectionist and goes against obligations the United States has to the WTOUS citizen will have mixed results when attempting to make a deposit to an online gambling site with a credit or debit card. The transaction will usually be processed with no problems, but occasionally it will be rejected. If your deposit is rejected, don't worry that federal agents will show up at your door. It just means you will have to find a different way to get your money to your player account.
We are not lawyers, this is just an opinion of research.  If you have questions regarding gambling on the internet, please consult the advise of an attorney.

Reference:

http://en.wikipedia.org/wiki/SAFE_Port_Act

The Security and Accountability For Every Port Act of 2006 (or SAFE Port Act, Pub.L. 109-347[1]) was an Act of Congress in the United States covering port security and to which an online gambling measure was added at the last moment. The House and Senate passed the conference report on September 30, 2006, and President Bush signed the Act into law on October 13, 2006 

http://en.wikipedia.org/wiki/World_Trade_Organization

The World Trade Organization (WTO) is an organization that intends to supervise and liberalize international trade. The organization officially commenced on January 1, 1995 under the Marrakech Agreement, replacing the General Agreement on Tariffs and Trade (GATT), which commenced in 1948. The organization deals with regulation of trade between participating countries; it provides a framework for negotiating and formalizing trade agreements, and a dispute resolution process aimed at enforcing participants' adherence to WTO agreements which are signed by representatives of member governments and ratified by their parliaments.^[4][5] Most of the issues that the WTO focuses on derive from previous trade negotiations, especially from the Uruguay Round (1986-1994).