平和に満足している人は、幸せである。

、。

Those who are content with peace are happy.

Literal

Peace [with-に] satisfied being person [topic-は], happy is.

平和に満足している人 is a relative clause: 'a person who is satisfied with peace.' 幸せである declares them happy using the formal copula. This reads like a philosophical or religious statement — aphoristic in tone.