Instead, Simpson used a "substantial degree of deference" to one of the three branches of the state government, the Republican-controlled General Assembly that passed the law in March.
Simpson, in his 68-page ruling, said strict scrutiny might have led him to a different conclusion.
You'll be seeing that again.
A coalition of attorneys who brought the legal challenge to the voter-ID law in May said they would file an appeal Thursday with the state Supreme Court. Jennifer Clarke of the Public Interest Law Center said the appeal would ask for an expedited ruling on the case.
"The Supreme Court, when it wants to, can act very quickly," Clarke said Wednesday. "If it wanted to, the Supreme Court could have this briefed within the next two weeks and resolved within the next month."
The Supreme Court usually has seven justices hearing appeals. Justice Jane Orie Melvin was suspended in May after being charged with using her state staff to run her campaigns.
That leaves the court with six justices - three Republicans and three Democrats. A tie vote on an appeal would leave Simpson's ruling in place.
It is still not clear how many voters in Pennsylvania lack the type of identification needed to vote. The Department of State has put the number as low as 1 percent and as high as 9 percent.
Simpson guessed the number was somewhere in the middle.
Lawyers who brought the legal challenge noted that 1 percent of the state's population eligible to vote would be 89,000 people. So the number of people impacted could be substantially higher.
Simpson's ruling repeatedly mentions a new state voter-ID card being developed by the Department of State but not yet available.
Ron Ruman, a department spokesman, said the card would be available starting Aug. 27. Voters would be able to get the new identification for free at PennDOT driver's license centers by swearing that they can't get other state-approved identification for voting, Ruman said.
Simpson's ruling was hailed by Republicans as a victory for safeguarding elections and derided by Democrats as a partisan effort to disenfranchise voters.
Secretary of State Carol Aichele said the law would "enhance confidence in our elections." Attorneys representing Aichele's office in the legal challenge admitted in court that they had no proof of in-person voter fraud occurring in the state.
State Rep. Mike Turzai, the House Majority Leader, said the law was an "important tool" against voter fraud.
Turzai, speaking at a Republican State Committee meeting in June, said the voter-ID law would help Mitt Romney defeat President Obama in Pennsylvania in the Nov. 6 presidential election.
Simpson called that statement "disturbing" and "boastful" but not proof that the law was motivated by partisan politics.
Obama's campaign in Pennsylvania vowed to educate voters about the new law.
City Commission chairwoman Stephanie Singer, Philadelphia's top election, emailed political supporters about a fundraiser she was holding Wednesday evening, writing that "our hopes of even delaying the law have decreased to extremely slim."
Contact Chris Brennan at 215-854-5973 or firstname.lastname@example.org. Follow on Twitter @ChrisBrennanDN. Read his blog, www.phillyclout.com.