During his confirmation hearing, Jeff Sessions took the following position:
During one of the key exchanges of the day, Senator Feinstein pressed the proven pro-lifer about abortion and whether he would deny access to victims of human trafficking, since those funds are all under the purview of the DOJ. Immediately, Sessions drew the line, insisting that his duty wasn't to write the law–but enforce it. "...Ultimately," he replied, "It's a matter for this United States Congress, not so much a matter for the attorney general. We need to put our money out to assist in this activity according to the rules established by the Congress." Feinstein pressed more, asking if he still believed Roe v. Wade was one of the worst Supreme Court rulings of all time. "It is," he answered truthfully. "I believe it violated the Constitution and really attempted to set policy and not follow law." Even so, he went on, "It is the law of the land... and I would respect it and follow it."
It's true that judicial rulings generally have the force of law. That's because judicial rulings are supposed to have a basis in law. There's an underlying law (e.g. the Constitution, statutory law). It's not a legal opinion out of thin air.
But let's pass on that for now. Let's grant for the sake of argument that Roe v. Wade is the "law of the land". In that event, what would it mean for DOJ for "follow" it or "enforce" it?
Let's put in this way: what does it mean to break a law? Generally, there are two kinds of laws: laws that mandate particular behavior and laws that prohibit particular behavior. To break a law is either to do what's prohibited or fail to do what's mandated. To enforce the law would be to punish a violator for breaking the law in one of those two respects (prescription or proscription).
Suppose there's a law mandating car insurance. To enforce the law might be to fine a driver who has no proof of insurance (if that's the prescribed penalty).
Suppose there's a law prohibiting the sale of narcotics. To enforce the law might be to arrest the dealer and charge him with breaking that law.
Assuming that Roe v. Wade is law, what is there for DOJ to enforce? How does someone break that law?
Even if abortion is deemed to be a legal right, that doesn't compel anyone to perform abortions–any more than the Second Amendment (which is a bona fide Constitutional right) compels anyone to sell guns.
Someone blocking the entrance to an abortion clinic might violate the law, but his infraction is already covered under trespassing.