Stephen Miller, who is the top immigration advisor to President-elect Donald Trump, has pledged that the incoming administration will begin its promised mass deportation campaign at “light speed” shortly after Trump’s inauguration. But there are several significant legal impediments that could frustrate those deportations.The Washington Post reported Friday that Trump’s Immigration and Customs Enforcement (ICE) will have some difficulty deporting at least of the roughly 1.4 million undocumented immigrants currently in the deportation queue next year. This includes those immigrants’ home countries refusing to take them, immigrants serving prison terms and other immigrants getting reprieves from judges due to medical conditions or other factors.Those obstacles could be just the beginning of the second Trump administration’s headaches in enacting its deportation agenda, as other unforeseen logistical barriers could tie up ICE agents in myriad other ways. One example is the military planes that ICE would rely on to fly migrants out of the country being unavailable due to aircraft already being committed elsewhere.READ MORE: ‘Going to pay a lot more’: Here’s how Trump’s deportations will lead to huge tax increases“If you start using those planes for deportations, you quickly get into problems with military force readiness,” an unnamed retired ICE official told the Post. “It’s the same contractors who are flying our service members to the Middle East or to Germany.”Tom Homan, who the president-elect has tapped as his incoming border czar, is tasked with heading up his deportation agenda. He’s promised that any undocumented immigrant that an immigration judge has cleared for deportation should be deported, regardless of whether they’ve committed a crime.“If those orders aren’t executed or carried out, then what the hell are we doing?” Homan said in November. “Nothing in immigration law says you need to commit a very serious criminal offense to be removed from the country.”Should Trump succeed in his stated goal of deporting millions of undocumented immigrants, it could inadvertently create a new financial headache for taxpayers. Journalist David Cay Johnston pointed out last month that any undocumented immigrant who has had a child since arriving in the United States would be separated from their children if deported, as their children are U.S. citizens. He then observed that foster care systems in multiple states could be overwhelmed, leading to significant property tax increases down the road.READ MORE: ‘Wait until 2025’: Trump’s former ICE chief makes chilling promise at far-right conferenceClick here to read the Post’s full report (subscription required).