Facebook says it should not be held liable under child protection laws for use of its ubiquitous “Like” button by Web users under the age of 13 on websites other than Facebook. Further, the company says, a Facebook “like” is tantamount to free speech, and that limitations on the use of the “Like” button would violate the U.S. Constitution.

Presented in a 20-page letter (PDF) to the U.S. Federal Trade Commission (FTC) last week, Facebook’s assertions come in response to proposed changes to the Children’s Online Privacy Protection Act (COPPA) that would expand the definition of the word “operator” in the law. The social network argues that such a change could include “plugin providers,” such as Facebook. The problem, says Facebook, is that the rule change could potentially make all plugin providers “responsible for the actions and motivations” of third-party websites of which companies like Facebook have no control.

Moreover, says Facebook, social plugins are “widely used by educational sites,” and imposing greater monitoring of plugin usage would impose “burdensome compliance obligations” on these sites, which often lack the resources to do so.

“Requiring these sites or services and plugin providers to monitor each others’ information practices could result in the eradication of integrated plugins and the powerful features they facilitate,” wrote Facebook.

In addition to the financial strain placed on educational sites and plugin providers, the proposed changes to COPPA fail to clarify the burden of responsibility, says Facebook, which in turn “is likely to create serious disincentives against growth in Internet technologies.”

Facebook also argues in the letter that limiting children’s ability to click a “Like” button “would infringe upon their constitutionally protected right to engage in protected speech.”

As currently written, COPPA prohibits the collection of personal data of Web users under the age of 13 without explicit parental consent. Because of this, Facebook (and many websites and online services) expressly forbid pre-teens from signing up. Despite Facebook’s rules, an estimated 5.6 million children under 13-years-old have Facebook profiles. Facebook reportedly deleted the accounts of 800,000 pre-teens over the past year, according to a June study by Consumer Reports.

The FTC’s proposed rule changes (PDF) would expand COPPA to apply to not only websites, but all “online services,” including mobile apps, games, and online advertising networks. The changes would also limit the use of Web cookies, which track Web users’ online activities. Further, the changes would expand the definition of personal information to include IP address and geolocation data.

Facebook has reportedly been working on ways to allow for children under 13 to have profiles that are COPPA-compliant.