In 2007, Sleisenger began his private criminal law practice, with an emphasis on serving clients with federal appellate and trial matters, as well as asset forfeiture, an integral part of criminal law enforcement which includes the seizure and subsequent administrative, civil, and criminal law proceedings where the government seeks to forfeit real property and proceeds of more than 200 different state and federal crimes, allegedly used to commit or facilitate the commission of drug crimes, money laundering, violent crimes, public corruption, RICO, terrorism, and other U.S. Code violations. Sleisenger has represented clients throughout the U.S., as well as clients residing or engaged in business in foreign countries.

Trial and appellate practice areas have included white collar criminal defense, narcotics trafficking, money laundering and reporting offenses, public corruption, racketeering (RICO), bank fraud and related financial crimes, access device, identity and computer fraud, immigration crimes, mail fraud, health care fraud, tax fraud, counterfeiting, bank robbery, firearms offenses, grand theft, theft of government property, threats against federal officers, perjury and false statement, and child pornography. Sleisenger has also dealt with witness immunity, witnesses called before the Grand Jury, and internal investigations involving terrorism and invasion of privacy in the entertainment industry.