Preface to the Book of Church Order

Section 2 : The Preliminary Principles
Paragraph 2 : Terms of Communion

2. That, in perfect consistency with the above principle of common right, every Christian church, or union or association of particular churches, is entitled to declare the terms of admission into its communion, and the qualifications of its ministers and members, as well as the whole system of its internal government which Christ hath appointed: that, in its exercise of this right it may, notwithstanding, err, in making the terms of communion either too lax or too narrow; yet, even in this case, it does not infringe upon the liberty or the rights of others, but only makes an improper use of its own.

Footnote: Confession of Faith, Chapters 20 & 25. [as per M4GA, Appendix J, p. 203]

DIGEST :

BACKGROUND & COMPARISON:
PCA 1973, Adopted text, as printed in the Minutes of General Assembly, page 128
That, in perfect consistency with the above principle of common right, every Christian church, or union or association of particular churches, is entitled to declare the terms of admission into its communion, and the qualifications of its ministers and members, as well as the whole system of its internal government which Christ hath appointed: that, in its exercise of this right it may, notwithstanding, err, in making the terms of communion either too lax or too narrow; yet, even in this case, it does not infringe upon the liberty or the rights of others, but only makes an improper use of its own.

Continuing Presbyterian Church 1973, Proposed text, Preface, Preliminary Principles, paragraph 2
That, in perfect consistency with the above principle of common right, every Christian church, or union or association of particular churches, is entitled to declare the terms of admission into its communion, and the qualifications of its ministers and members, as well as the whole system of its internal government which Christ hath appointed: that, in its exercise of this right it may, notwithstanding, err, in making the terms of communion either too lax or too narrow; yet, even in this case, it does not infringe upon the liberty or the rights of others, but only makes an improper use of its own.

1866 PCUS draft, paragraph 2:
That,

[Note: The Preliminary Principles appeared solely in the 1866 draft of the PCUS Form of Government, as reported and published in The Christian Observer, vol. 45, nos. 40 & 41 (4 Oct. & 11 Oct. 1866). Inclusion of the Principles was rejected when the PCUS Assembly met in 1867.]

Commentary :
Hodge, J. Aspinwall, What Is Presbyterian Law? (Philadelphia, 1882, pp. 23-24) :
II. What is the second principle?
"Every Christian Church, or union or association of particular churches, is entitled to declare the terms of admission into its communion, and the qualifications of its Ministers and members, as well as the whole system of its internal government which Christ hath appointed." This principle is essential to all organizations. Men are at liberty to refuse to be connected with a society, but if they voluntarily enter, they must submit to its terms of admission and to its laws. So if any man's conscience will not permit him to concur with, or passively submit to, the standards of the Church, he "shall, after sufficient liberty modestly to reason and remonstrate, peaceably withdraw from our communion, without attempting to make any schism." Provided that which he cannot accept shall be judged by the Church to be indispensable to Presbyterian doctrine or polity.[1] This of course refers only to the officers of the Church, who are required to receive and adopt the standards of the Church.[2] But communicants are received on profession of faith in the Lord Jesus.[3]
May the Church err in the exercise of this right?
Churches, "in the exercise of this right, may, notwithstanding, err in making the terms of communion either too lax or too narrow ; yet even in this case they do not infringe upon the liberty or the rights of others, but only make an improper use of their own."
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[1] Presbyterian Digest, p. 48.
[2] Form of Government [PCUSA], chs. xiii. and xv.
[3] Directory for Worship [PCUSA], ch. ix. ; Presbyterian Digest, p. 307. See p. 135.