"social Magisterium"?
He is talking about two Catholic principles that few people recognize. The Pope wrote about them in an encyclical, but no one picked up on it.
They are subsidiarity and solidarity. Subsidiarity means going to the lowest form of government — even the church — or local government — to have a problem scrutinized.
Solidarity connotes common sense approach to everything. There is more on these two principles in some of the links below.
Paul Ryan urges Catholics to act before religious freedoms erode
Dolan: Ryan Is a Great Public Servant (great insight into Ryan's views)
Paul Ryans Bishop Defends Him Amid Attacks on His Application of Church Teaching
Paul Ryan, Catholic Who Looks to Church's Social Teaching, Tapped as Romney Running Mate
The other Ryan: the candidates wife, Janna
Paul Ryan, Joe Biden, and Liberal False Equivalence
Ryan as VP Pick Continues Election Year Focus on Catholicism
Paul Ryan Faces Left-Wing Religious Attack
Life, Liberty, and the Pursuit of Holiness (Paul Ryan)
Paul Ryan: Midwesterner, Catholic, intellectual