The counsel general criticised the decision to close ten law courts across Wales in a speech at Cardiff University's school of law on Thursday.
"The rule of law is meaningless if there is no access to justice," he said.
The Ministry of Justice said access to justice "is not about proximity to a court".
Ten courts including Brecon, Bridgend, Neath Port Talbot, Pontypridd and Wrexham are closing under government plans.
Mr Antoniw, AM for Pontypridd and the Welsh Government's senior legal advisor, said: "In post war Britain access to justice and the administration of justice has never been so limited and restricted."
"It is pointless to be granted rights if you have no way of enforcing them," he said.
"The abolition of legal aid for the majority of people in the areas of social welfare law, family law, housing and debt, is more than a mere restriction of access to justice."
"The changes we have experienced in the past few years represent an end to the ideological consensus between political parties across the UK reached in 1945 that access to justice is a fundamental social and human right and an imperative in the building of a fairer and more equal society," Mr Antoniw said.
He said another principle of access to the law is that courts and tribunals should be based in local communities with "judges, magistrates and tribunal chairs who know and understand the community".
"The recently announced closure of another ten court buildings in Wales is another nail in the coffin of this principle," the minister added.
A Ministry of Justice spokesman said: "Access to justice is not about proximity to a court, and we are investing over Â£700m in reforming our courts to deliver swifter and more certain justice.
"The decision to close a court is never taken lightly, but maintaining underused and dilapidated court buildings is unsustainable, costing the taxpayer Â£500m a year."
UK government cuts to justice threaten human rights, Labour AM Mick Antoniw has said.