Four years after passing a controversial doctrinal "Statement of Scriptural and Confessional Principles" by simple majority vote of convention delegates, the convention of the Lutheran Church-Missouri Synod has approved a detailed procedure governing adoption of such statements in future.

By-law changes approved by the convention in a show-of-hands vote require approval by two-thirds of congregations that respond within six months to doctrinal statements approved by majority vote at conventions. Without that congregational ratification, the statements are inoperative.

The resolution distinguishes between doctrinal resolutions and doctrinal statements. The former may be approval "for the information, counsel and guidance of te membership" by a convention majority, while "doctrinal statements set forth in greater detail the corporate position of the Synod especially in controverted matters," according to the resolution.

The convention extended into 1978 the time during which Synod congregations, pastors and teachers may belong to the newly formed Association of Evangelical Lutheran Churches (AELC).

Under a resolution adopted by an estimated 3-to-1 majority, such dual membership will be allowed until 30 days before conventions of the Synod's districts, held at various times during early 1978.

The previous Synod cutoff date for dual membership was Sept. 1. The AELC was organized formally last year by some who disagree with the Synod's direction since the 1969 election of Dr. J.A.O. Preus as president.

In other actions, the convention urged delay in publication of a proposed inter-Lutheran worship book that grew out of a resolution of the Synod's convention in 1965.

Acting after much debate, delegates said theological questions that have surfaced in the Synod about some portions of the proposed book require a special committee to conduct a thorough review of the volume.

Leaders of the other three bodies - the American Lutheran Church. Lutheran Church in America, and Evangelical Lutheran Church of Canada - have indicated that having completed their review of the proposed materials, they will likely publish the book by the end of 1978, regardless of what the Synod does.