D. A. Orr in the Oxford Dictionary of National Biography tentatively identifies him with the John March admitted to the degree of B.C.L.
27 November 1632, as a member of St. Edmund Hall, Oxford; and more confidently with the John March of Barnard's Inn in 1635, of Gray's Inn in 1636, and called to the bar in June 1641.
[1] An Argument or Debate in Law of the great question concerning the Militia (1642) by March argued the legality of Parliament's moves to raise troops.
On 20 August 1649 the Council of State nominated him as one of four commissioners to go to Guernsey; three years later (6 April 1652) he was chosen by the Council of State to Scotland, with three others to administer justice in the courts.
[1][2] In 1656 March seems to have been acting as secretary or treasurer to the trustees for the sale of crown lands at Worcester House.