"Protecting liberty is about protecting freedoms against both known and future threats. Some may argue that we can surely trust a democratically-elected government in Australia to never try to introduce more widespread censorship. I am not so sure!," said Hockey.
"One of our main concerns is how the list might expand in the future," said EFA vice-chair Colin Jacobs.
"With pressure from the media and special interest groups, it's hard to imagine this government forever resisting the temptation to add to the list - let alone all future governments," he added.
Hockey was seen as a potential party leader in the run-up to Tony Abbott's ascension to the role, and is widely regarded as a moderate with broad appeal to the electorate.
EFA campaign manager Peter Black said "Mr Hockey correctly identified several of the fundamental problems in the Government's mandatory Internet filtering policy."
"Most importantly that the filter will not stop children from accessing inappropriate content and will not prevent criminals from accessing and distributing sexual abuse material," he added.
"Parental supervision is actually the most effective way to protect children from accessing inappropriate content."
EFA officials expressed the hope that other coalition members will follow Hockey's example and conclude that increased education and law enforcement would be better than censorship.
To that end, the organisation launched its Lobby a Lib campaign this week, calling on individuals who share EFA's concern about filtering to encourage Liberal MPs and senators to vote against the proposal.
On the other hand, a leading opponent of the (EFA backed) push to introduce an R18+ category for games is Michael Atkinson, Attorney-General in the South Australia's Labor Government.