David Bernstein at Volokh sketches out his argument for how the Court can hold that the Privileges or Immunities Clause protects a right to bear arms:

(a) the Court should take this opportunity to start to move its individual rights jurisprudence from the Due Process Clause to the P or I Clause;
(b) The problem with the D.P. Clause is that it traditionally prohibits “arbitrary” infringements on liberty, but arbitrariness is in the eye of the beholder, as is what is meant by “liberty,” see in both contexts Roe v. Wade;
(c) worse yet, cases like Roe fail to give any real weight to the police power, the traditional brake on the D.P. Clause;
(d) by contract, through historical investigation, we can determine with some precision what rights were considered privileges or immunities of citizens.  Abortion, (right to die, etc.) was not one of them!;
(e) Justice Field and Justice Bradley were correct in their SlaughterHouse dissents that one p or i of citizenship is the right to pursue an occupation  free from government-sponsored monopoly, a much narrower right than the later Lochner due process right to be free from arbitrary restrictions on liberty of contract, and a right that goes way back in Anglo-American history;
(f) the ultimate holding of SlaughterHouse was still correct, because Louisiana had a legitimate police power interest in ensuring that its waterways didn’t carry disease, and the butchers who sued weren’t driven out of the profession, they just had to work in the safe location dictated by the government.

Our article, in the Georgetown Journal of Law & Public Policy, titled Opening Pandora’s Box? Privileges or Immunities, The Constitution in 2020, and Properly Incorporating the Second Amendment touches (a), (b), (d).

David seeks to appeal “not just to originalism, but to the conservatives’ long-term political self-interest, and affinity for the conservative political coalition that put them in power.” This is precisely the tact we take.

The Court today more-or-less has 5 solid votes for incorporation. But as Justice Stevens and Ginsburg leave the Court, and Justice Scalia and Kennedy age, President Obama has the potential to totally transform the Judiciary. A future court could easily recognize a constitutional right to positive rights such as health care or social equality. Thus, we propose that the Court look to rights held as privileges or immunities during the time of Reconstruction, and not an evolving standard of rights (as articulated in Balkin’s work, and the Constitution in 2020 Project). If the Conservative majority takes a stand now, they can preserve an originalist jurisprudence for the forseeable future. If they punt, and let future Courts handle this, they are just waiting for Pandora’s Box to be opened.